Epitaxially grown ferroelectric thin films for agile devices

Agile devices based on ferroelectric material thin films provide a promising approach to solve the problem of multi-standard communication systems. As an alternative to BaxSr1− x TiO3, the potentialities of two other materials, namely SrBi2Nb2O9 and KTa1− x Nb x O3 have been explored. This review gets an insight into the growth of thin films of these materials, including the control of stoichiometry and of their orientation on various substrates usable in the microwave range. Dielectric measurements show that the Curie temperature is close to the value reported on bulk materials and that the transition is of first order, while the Curie-Weiss temperature is frequency dependant in the example of KNbO3 films. Microwave test devices, patterned on such films, show promising agility levels, while it appears that further efforts have to be done to reduce the dielectric losses.